• Title/Summary/Keyword: 슬러그 유동

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Prediction of Two-phase Taylor Flow Characteristics in a Rectangular Micro-channel (사각 마이크로 채널 내 Taylor 유동 특성 예측에 대한 연구)

  • Lee, Jun Kyoung;Lee, Kwan Geun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.7
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    • pp.557-566
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    • 2015
  • The characteristics of a gas-liquid Taylor (slug) flow in a square micro-channel with dimensions of $600{\mu}m{\times}600{\mu}m$ are experimentally investigated in this paper. The test fluids were nitrogen and water. The superficial velocities of the liquid and gas were in the ranges of 0.01 - 3 m/s and 0.1 - 3 m/s, respectively. The bubble and liquid slug lengths, bubble velocities, and bubble frequencies for various inlet conditions were measured by analyzing optical images obtained with a high-speed camera. It was found that the measured values (bubble and liquid slug lengths, bubble velocities) were not in good agreement with the values obtained using empirical models presented in the existing literature. Modified models for the bubble and liquid slug lengths and bubble velocity are suggested and shown to be in good agreement (${\pm}20$) with the measured values. Moreover, the bubble frequency could be predicted well by the relationship between the unit cell length and its velocity.

Measurement of the Void Fraction of Slug and Bubbly Flows Using Three-Ring Impedance Meters (3-ring 임피던스미터를 이용한 슬러그류 및 기포류의 기공률 측정)

  • Kim, Jong-Rok;Ahn, Yeh-Chan;Kim, Moo-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.1
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    • pp.83-88
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    • 2012
  • Real slug and bubbly flows were measured using a three-ring impedance meter that can efficiently measure the void fraction of two-phase flows in a tube. First, the fitting curves between the signal from the impedance meters and the void fraction were found. The impedance meter had different fitting curves for slug and bubbly flows that had the same void fraction. An impedance meter should choose one of the two fitting curves according to the flow pattern, and the flow patterns can be recognized using the measured void fraction. The velocities and sizes of the bubbles were calculated using the void fraction curves measured by two impedance meters.

Effect of Gas- and Liquid-injection Methods on Formation of Bubble and Liquid Slug at Merging Micro T-junction (마이크로 T자형 합류지점에서 기체 및 액체의 주입 방법이 기포 및 액체 슬러그 생성에 미치는 영향)

  • Lee, Jun Kyoung;Lee, Chi Young
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.4
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    • pp.227-236
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    • 2016
  • In the present experimental study, the effect of gas- and liquid-injected methods on the formation of bubble and liquid slug at the merging micro T-junction of a square microchannel with dimensions $600{\mu}m{\times}600{\mu}m$ was investigated. Nitrogen and water were used as test fluids. The superficial velocities of the liquid and gas were in the range of 0.05 - 1 m/s, and 0.1 - 1 m/s, respectively, where the Taylor flow was observed. The bubble length, liquid slug length, bubble velocity, and bubble generation frequency were measured by analyzing the images captured using a high-speed camera. Under similar inlet superficial velocity conditions, in the case of gas injection to the main channel at the merging T-junction (T_gas-liquid), the lengths of the bubble and liquid slug were longer, and the bubble generation frequency was lower than in the case of liquid injection to the main channel at the merging T-junction (T_liquid-gas). On the other hand, in both cases, the bubble velocity was almost the same. The previous correlation proposed using experimental data for T_liquid-gas had predicted the present experimental data of bubble length, bubble velocity, liquid slug length, and bubble generation frequency for T_gas-liquid to be ~24%, ~9%, ~39%, ~55%, respectively.

Slug Characteristics in a Bubbling Fluidized Bed Reactor for Polymerization Reaction (기포유동층 고분자 중합 반응기에서의 슬러그 특성)

  • Go, Eun Sol;Kang, Seo Yeong;Seo, Su Been;Kim, Hyung Woo;Lee, See Hoon
    • Korean Chemical Engineering Research
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    • v.58 no.4
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    • pp.651-657
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    • 2020
  • Fluidization processes in which solid particles vividly move like gas or liquid have been widely used in various industrial sectors, such as thermochemical energy conversion and polymerization processes for general purpose polymer resins. One of the general purpose polymer resins, LLDPE(Linear low-density polyethylene) resins have been produced in bubbling fluidized bed processes in the world. In a bubbling fluidization polymerization reactors, LLDPE particles with relatively larger particle size and low density are fluidized by hydrogen gas for polymerization reaction. Though LLDPE polymerization reactors are one of bubbling fluidization processes, slugs that have negative impact for reaction exist or occur in these processes. Therefore, the fluidization state of LLDPE particles was investigated in a simulation model similar to a pilot-scale polymerization reactor (0.38 m l.D., 4.4 m High). In particular, the effect of gas velocity (0.45-1.2 m/s), solid density (900-199 kg/㎥), solid sphericity (0.5-1.0), and average particle size (120-1230 ㎛), on bed height and fluidization state were measured by using a CPFD(Computational particle-fluid dynamics) method. With CPFD analysis, the occurrence of a flat slug was visualized. Also, the change in particle properties, such as particle density, sphericity, and size, could reduce the occurrence of slug and bed expansion.

Mass Transfer Characteristics of the Carbon Dioxide-Water Slug Flow in Vertical Small-Bore Tubes (작은 직경의 수직관을 흐르는 이산화탄소-물 슬러그 유동의 물질전달 특성)

  • Lee, Kyung-Jae;Kim, Dong-Seon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.5
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    • pp.401-408
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    • 2012
  • Volumetric mass transfer coefficient was measured with carbon dioxide and deionized water for the gas-liquid cocurrent slug flow in 2, 5 and 8 mm tubes. Measurement was repeated with and without a vertical section in an experimental setup and entrance effect was found greater for smaller tubes. Volumetric mass transfer coefficient in the vertical section was found generally a strong function of gas- and liquid-phase superficial velocities. 5 mm- and 8 mm-tube data are highly consistent each other but not with 2 mm tube.

Measurement of the Void Fraction in Slug Flow using an Optical Method (광학적 방법을 이용한 슬러그 유동의 기공률 측정)

  • Kim, Dong-Seon
    • Journal of Institute of Convergence Technology
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    • v.1 no.2
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    • pp.25-28
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    • 2011
  • Void fraction has been measured for the gas-liquid cocurrent slug flow in 8mm vertical acrylic tube using an optical method. Bubble speed, length and period could be measured with the two sets of laser-infrared sensor modules mounted 25mm apart alongside the tube, which were designed to detect variation of light intensities with a time delay when two parallel laser beams were refracted successively by a passing bubble. It was found that the results were in good agreement with the previous studies in the literature suggesting that the method used in this study were sound and accurate.

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Semi-Empirical Analysis of the Mass Transfer Characteristics of the Slug Flow in Vertical Mesoscale Tubes (작은 수직관을 흐르는 슬러그 유동의 물질전달 특성에 대한 반경험적 해석)

  • Kim, Dong-Seon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.8
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    • pp.366-374
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    • 2014
  • Experimental mass transfer data, which were obtained for the $CO_2$-water slug flows in vertical tubes with 2, 5, and 8mm diameters, were analyzed in comparison with the penetration theory. It was found that a penetration model with molecular diffusion coefficient cannot predict the experimental data accurately. An effective diffusion coefficient, which considers enhancement effect of interfacial waves, was suggested to improve prediction. Another empirical factor was also suggested to consider the effect of non-uniform interface velocity. A modified penetration model was found to be capable of predicting the experimental data reasonably well.

Study on the Characteristics of Bubble and Liquid Slugs for Gas-Liquid Taylor Flow in a Rectangular Micro-channel (사각 마이크로 채널 내 Taylor Flow의 기포 및 액체 슬러그 유동 특성에 대한 연구)

  • Lee, Jun Kyoung;Lee, Kwan Geun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.10
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    • pp.520-526
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    • 2015
  • The characteristics of gas-liquid Taylor (Slug) flow in a square micro-channel of $600{\sim}600{{\mu}m}$ were investigated experimentally in this paper. The test fluids were nitrogen and water. The liquid and gas superficial velocities were 0.01~3 m/s and 0.1~3 m/s, respectively. Bubble and liquid slug length, bubble velocity, and frequency were measured by analyzing optical images using a high speed camera. Bubble length decreased with higher liquid flow rate, which increased dramatically with higher gas flow rate. However, slug length did not vary with changes in inlet liquid conditions. Additionally, bubble velocities and frequencies increased with higher liquid and gas flow rates. It was found that measured bubble lengths were in good agreement with the empirical models in the existing literature, but slug lengths were not.

Flow Characteristics of a Gas-Liquid Slug Flow in Small Vertical Tubes (작은 수직관을 흐르는 기-액 슬러그 유동의 유동특성)

  • Kye, Seok-Hyun;Kim, Dong-Seon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.25 no.5
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    • pp.246-254
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    • 2013
  • Some characteristics of nitrogen-water slug flow were optically measured, in vertical acrylic tubes of 2, 5 and 8 mm diameter. Bubble velocity, bubble and unit cell lengths were measured, by analyzing the light intensity signals from two sets of dot laser-infrared sensor modules mounted along the transparent tubes. Optical images of the bubbles were also taken and analyzed, to measure bubble shapes and liquid film thickness. It was found that the measured bubble velocities were in good agreement with the empirical models in the literature, except for those measured under high superficial velocity condition in the 2 mm tube. Bubble length was found to be the longest in the 2 mm tube, being 4 to 5 times those of the other tubes. Liquid film was found to have developed early in the 2 mm tube, which made the blunt shape of the bubble head. Liquid film thickness in the 8 mm tube was measured at almost twice those of the other tubes.

CFD Modeling of Unsteady Gas-Liquid Flow in a Small Scale Air-Lift Pump (소형 공기 양수 펌프의 불규칙한 가스-액체 흐름의 CFD 모델링)

  • Li, X.S.;Jeong, H.M.;Chung, H.S.
    • Journal of Power System Engineering
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    • v.16 no.1
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    • pp.30-37
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    • 2012
  • 공기 양수 펌프는 재생 에너지 분야, 부식 및 마모 특성의 유체의 활용 등 높은 신뢰성과 낮은 유지보수 비용을 필요로 하는 분야에서 그 사용이 증대되고 있다. 본 연구에서는 소형 공기 양수 펌프의 성능 평가 및 기초 데이터를 얻기 위한 연구로, D=0.012~0.019m, L=0.933m인 배관의 침수 깊이(${\beta}$=0.55,0.60,0.65,0.70)에 따른 수치해석을 수행하였다. 수치 해석 및 실험 결과는 유사성을 뛰었으며, 펌프의 사양과 효율은 공기의 질량 유속 비, 침수 깊이 비와 양수 배관의 길이에 관한 함수로 나타났다. 그리고 최대 물과 공기 질량 유속의 비는 각 배관에서 서로 다른 침수 깊이의 비로 나타났으며, 공기 양수 펌프의 최대 효율이 발생되는 운전조건은 슬러그(slug)와 슬러그 교반 정도(slug-churn flow regime)에 따라 나타남을 알 수 있었다.